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Friday, August 3, 2012

Timeline of the Universe — A representation of the evolution of the universe over 13.7 billion years. The far left depicts the earliest moment we can now probe, when a period of “inflation” produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 380,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe. (Credit: NASA / WMAP Science Team)

Nothing is NegligibleWhy There is Something Rather than Nothing

by Michael Shermer
Why is there something rather than nothing? The question is usually posed by Christian apologists as a rhetorical argument meant to pose as the drop-dead killer case for God that no scientist can possibly answer. Those days are over. Even though scientists are not in agreement on a final answer to the now non-rhetorical question, they are edging closer to providing logical and even potentially empirically testable hypotheses to account for the universe. Here are a dozen possible answers to the question

The Definitive Dozen

1GOD. The theist’s answer to the question is that God existed before the universe and subsequently brought it into existence out of nothing (ex nihilo) in a single creation moment as described in Genesis. But the very conception of a creator existing before the universe and then creating it implies a time sequence. In both the Judeo-Christian tradition (along with the Babylonian pre-Judeo-Christian cosmogony) and the scientific worldview, time began when the universe came into existence, either through divine creation or the Big Bang. God, therefore, would have to exist outside of space and time, which means that as natural beings delimited by living in a finite universe, we cannot possibly know anything about such a supernatural entity. The theist’s answer is an untestable hypothesis and thus amounts to nothing more than a god-of-the-gaps argument.

2WRONG QUESTION. Asking why there is something rather than nothing presumes “nothing” is the natural state of things out of which “something” needs an explanation. Maybe “something” is the natural state of things and “nothing” would be the mystery to be solved. As the physicist Victor Stenger notes in his book, The Fallacy of Fine Tuning: “Current cosmology suggests that no laws of physics were violated in bringing the universe into existence. The laws of physics themselves are shown to correspond to what one would expect if the universe appeared from nothing. There is something rather than nothing because something is more stable.”

3GRAND UNIFIED THEORY. In order to answer the question, we need a comprehensive theory of physics that connects the subatomic world described by quantum mechanics to the cosmic world described by general relativity. As the Caltech cosmologist Sean Carroll notes in his book From Eternity to Here: “Possibly general relativity is not the correct theory of gravity, at least in the context of the extremely early universe. Most physicists suspect that a quantum theory of gravity, reconciling the framework of quantum mechanics with Einstein’s ideas about curved spacetime, will ultimately be required to make sense of what happens at the very earliest times. So if someone asks you what really happened at the moment of the purported Big Bang, the only honest answer would be: ‘I don’t know.’” That grand unified theory of everything will itself need an explanation, but it may be explicable by some other theory we have yet to comprehend out of our sheer ignorance at this moment in history.

4BOOM-AND-BUST CYCLES. Sean Carroll also suggests that our universe may be just one in a series of boom-and-bust cycles of expansion and contractions of the universe, with our universe just one “episode” of the bubble’s eventual collapse and re-expansion in an eternal cycle, and therefore “there is no such thing as an initial state, because time is eternal. In this case, we are imagining that the Big Bang isn’t the beginning of the entire universe, although it’s obviously an important event in the history of our local region.”

5DARWINIAN MULTIVERSE. According to the cosmologist Lee Smolin, in his book The Life of the Cosmos, our universe is just one of many bubble universes with varying sets of laws of nature. Those universes with laws of nature similar to ours will generate matter, which coalesces into stars, some of which collapse into black holes and a singularity, the same entity out of which our universe may have sprung. Thus, universes like ours give birth to baby universes with those same laws of nature, some of which develop intelligent life smart enough to discover this Darwinian process of cosmic evolution.

6INFLATIONARY COSMOLOGY. In his 1997 book The Inflationary Universe, the cosmologist Alan Guth proposes that our universe sprang into existence from a bubble nucleation of spacetime. If this process of universe creation is natural, then there may be multiple bubble nucleations that give rise to many universes that expand but remain separate from one another without any causal contact between them.

7MANY-WORLDS MULTIVERSE. According to the “many worlds” interpretation of quantum mechanics, there are an infinite number of universes in which every possible outcome of every possible choice that has ever been available, or will be available, has happened in one of those universes. Thismany-worlds multiverse is grounded in the bizarre findings of the famous “double-slit” experiment, in which light is passed through two slits and forms an interference pattern of waves on a back surface (like throwing two stones in a pond and watching the concentric wave patterns interact, with crests and troughs adding and subtracting from one another). The spooky part comes when you send single photons of light one at a time through the two slits—they still form an interference wave pattern even though they are not interacting with other photons. How can this be? One answer is that the photons are interacting with photons in other universes! In this type ofmultiverse you could meet your doppelgänger, and depending on which universe you entered, your parallel self would be fairly similar or dissimilar to you, a theme that has become a staple of science fiction (see, for example, Michael Crichton’s Timeline).

8BRANE UNIVERSES. A multi-dimensional universe may come about when three-dimensional “branes” (a membrane-like structure on which our universe exists) moves through higher-dimensional space and collides with another brane, the result of which is the energized creation of another universe.

9STRING UNIVERSES. A related multiverse is derived through string theory, which by at least one calculation allows for 10500 possible worlds, all with different self-consistent laws and constants. That’s a 1 followed by 500 zeroes possible universes (12 zeroes is a trillion!). In his book The Unconscious Quantum, Victor Stenger published the results of a computer model that analyzes what just 100 different universes would be like under constants different from our own, ranging from five orders of magnitude above to five orders of magnitude below their values in our universe. Stenger found that long-lived stars of at least 1 billion years—necessary for the production of life-giving heavy elements—would emerge within a wide range of parameters in at least half of the universes in his model.

10QUANTUM FOAM MULTIVERSE. In this model, universes are created out of nothing, but in the scientific version of ex nihilo the nothing of the vacuum of space actually contains the theoretical spacetime mishmash called quantum foam, which may fluctuate to create baby universes. In this configuration, any quantum object in any quantum state may generate a new universe, each one of which represents every possible state of every possible object. This is Stephen Hawking’s explanation for the fine-tuning problem that he himself famously presented in his 1996 book (co-authored with Roger Penrose) The Nature of Space and Time: “Quantum fluctuations lead to the spontaneous creation of tiny universes, out of nothing. Most of the universes collapse to nothing, but a few that reach a critical size, will expand in an inflationary manner, and will form galaxies and stars, and maybe beings like us.”

11M-THEORY GRAND DESIGN. Stephen Hawking has continued working on this question, and this month, he and the Caltech mathematician Leonard Mlodinow present their answer in a book entitledThe Grand Design. They approach the problem from what they call “model-dependent realism,” based on the assumption that our brains form models of the world from sensory input, that we use the model most successful at explaining events, and that when more than one model makes accurate predictions “we are free to use whichever model is most convenient.” Employing this method, they write, “it is pointless to ask whether a model is real, only whether it agrees with observation.” The dual wave/particle models of light are an example of model-dependent realism, where each one agrees with certain observations but neither one is sufficient to explain all observations. To model the entire universe, Hawking and Mlodinow employ “M-Theory,” an extension of string theory that includes 11 dimensions and incorporates all five current string theory models. “M-theory is the most general supersymmetric theory of gravity,” Hawking and Mlodinow explain. “For these reasons M-theory is the only candidate for a complete theory of the universe. If it is finite—and this has yet to be proved—it will be a model of a universe that creates itself.” Although they admit that the theory has yet to be confirmed by observation, if it is, then no creator explanation is necessary because the universe creates itself. I call this auto-ex-nihilo.

12NOTHING IS UNSTABLE, SOMETHING IS NATURAL In his 2012 book, A Universe From Nothing, the cosmologist Lawrence M. Krauss attempts to link quantum physics to Einstein’s gravitational theory of general relativity to explain the origin of something (including a universe) from nothing: “In quantum gravity, universes can, and indeed always will, spontaneously appear from nothing. Such universes need not be empty, but can have matter and [electromagnetic] radiation in them, as long as the total energy, including the negative energy associated with gravity [balancing the positive energy of matter], is zero.” And: “In order for the closed universes that might be created through such mechanisms to last for longer than infinitesimal times, something like inflation is necessary.” Observations have revealed that, in fact, the universe is flat (there is just enough matter to eventually halt its expansion), its energy is zero, and it underwent rapid inflation, or expansion, shortly after the Big Bang as described by inflationary cosmology. Thus, Krauss concludes, “quantum gravity not only appears to allow universes to be created from nothing—meaning…the absence of space and time—it may require them. ‘Nothing’—in this case no space, no time, no anything!—is unstable.”

Putting Something to the Test

Many of these dozen explanations are testable. The theory that new universes can emerge from collapsing black holes may be illuminated through additional knowledge about the properties of black holes. Other bubble universes might be detected in the subtle temperature variations of the cosmic microwave background radiation left over from the Big Bang of our own universe. NASA recently launched a spacecraft constructed to study this radiation. Another way to test these theories might be through the Laser Interferometer Gravitational Wave Observatory (LIGO) that is designed to detect exceptionally faint gravitational waves. If there are other universes, perhaps ripples in gravitational waves will signal their presence. Maybe gravity is such a relatively weak force (compared to electromagnetism and the nuclear forces) because some of it “leaks” out to other universes. Maybe.
After a column I wrote in Scientific American on this topic (“Much Ado About Nothing,” May, 2012), I received an email from the Columbia University theoretical physicist Peter Woit cautioning me not to put too much emphasis on any one of these hypotheses/answers to the question of why there is something rather than nothing, noting that even these proposed tests probably themselves lack validity, if they could ever be conducted in reality. He explained that his skepticism came not out of religious conviction: “I’m as much of an atheist as anyone, and I’m really disturbed to see arguments being made that are going to end up discrediting skepticism and atheism.” He then posted a blog commentary on my Scientific American column, noting that my “authority here is the Hawking/Mlodinow popular book, but he’s also convinced that WMAP and LIGO are somehow going to provide evidence for multiverses, something that even the most far-out theorists in this field aren’t claiming.” Regarding my comment that perhaps gravity “leaks” out to other universes Woit responds: “Nobody seems to have told Shermer that this is not an idea taken seriously by a significant number of theorists, or that LHC data has shot down the hopes of the one or two such theorists.” Woit was prescient in that the prominent Intelligent Design creationist William Dembski did highlight Woit’s skepticism at his blog Uncommon Descent (“Serving the Intelligent Design Community”), quoting Woit and commenting: “Don’t nobody tell Shermer. It’s more fun this way.”
Given the fact that I appreciated Peter Woit’s skeptical book on string theory (Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law), I queried my sources. Physicist Victor Stenger responded: “The multiverse is not nonsense. It is based on good theory, but only theory. It is, in principle, detectable by measuring an anisotropy in the cosmic background radiation. That’s why I did not rely on it in The Fallacy of Fine-Tuning. I agree with Woit on M-theory, though.” Caltech physicist Leonard Mlodinow said he doubts that either he or Woit knows what “most physicists” think about the multiverse, and then opined that “most cosmologists certainly believe it,” recalling that Brian Greene “outlined the general thinking (as opposed to, say, Hawking’s particular views) very well in his book on it” (The Hidden Reality). Finally, Caltech physicist and cosmologist Sean Carroll noted: “You are completely correct, the multiverse is an idea that pops out of inflation (and string theory), not one that is put in out of desperation. Here is a column of my own making exactly this point. Carroll then cautioned: “Obviously the entire set of ideas is controversial and speculative, and should be presented as such, but it’s taken very seriously by a large number of extremely smart and respectable people.” For example: Leonard Susskind, Alex Vilenkin and Alan Guth (on the pro-multiverse side) and David Gross, Paul Steinhardt, and Edward Farhi (skeptical of the multiverse side).

God, Science, and the Great Unknown

In the meantime, while scientists sort out the science to answer the question Why is there something instead of nothing?, in addition to reviewing these dozen answers it is also okay to say “I don’t know” and keep searching. There is no need to turn to supernatural answers just to fulfill an emotional need for explanation. Like nature, the mind abhors a vacuum, but sometimes it is better to admit ignorance than feign certainty about which one knows not. If there is one lesson that the history of science has taught us it is that it is arrogant to think that we now know enough to know that we cannot know. Science is young. Let us have the courage to admit our ignorance and to keep searching for answers to these deepest questions.